Time of fall computer



y ym? March 30, 1954 M. TEN BOSCH El' AL TIME OF' FALL COMPUTER Filed Feb. l, 1950 mu Qn NQ QQ QM. WM.

ow wm udww QM Nana. x Y n Qwl lm w Patented Mar. 30, 1954 UNITED STATES PATENT OFFICE TIME OF FALL COMPUTER Application February 1, 1950, Serial No. 141,796

Claims.

Our invention relates to a time of fall computer and more particularly to a device for computing the time of fall of a bomb, torpedo, mine or other missile dropped from an aircraft.

Heretofore bombardiers found it necessary to compute the time of fall from a ballistic table having a large number of entries. Inasmuch as the ascertaining of the time of fall from the ballistic table took a period of time, it was necessary to enter the table with a predetermined altitude of release and to set the bombsight for the time of fall given by the ballistic table, taking into consideration the variable factors with the predetermined altitude as one of the arguments. If the bomb was not released at the predetermined altitude an error was introduced. Very frequently the necessity of avoiding antiaircraft lire rendered it inadvisable to approach a target at the predetermined altitude. Under the stress of action continuous errors are apt to be introduced in picking the time of fall from a ballistic table. The ballistic table has a large number of entries and the variation of the time of fall with respect to altitude would introduce a ymajor error into the time of fall.

We have discovered that it is an empirical fact that the ratio represented by bomb trail air speed altitude varies very slowly and that this ratio can be used together with altitude and vertical speed to compute time of fall. A variation of one hundred feet in altitude in this ratio has a negligible effect on the time of fall as compared with the variation of one hundred feet in the ballistic tables. The bomb trail is the distance measured on a horizontal line at ground level between the point of impact of the bomb and a point directly below the aircraft at the moment of impact.

One object of our invention is to provide a time of fall computer using as the ballistic the ratio bomb trail air speed X altitude Another object of our invention is to provide a time of fall computer-in which'time of fall is instantly given from 'settings representing altitude, ballistic and vertical velocity of the aircraft at the time of drop.

Another object of our invention is to provide a time of fall computer which is simple in construction, sure and easy of operation and which will continuously compute time of fall.

Other and further objects of our invention will appear from thefollowing description.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith:

Figure 1 is a diagrammatic view showing a time of fall computer according to one embodiment of our invention.

Figure 2 is a diagram showing the principle of operation of the quadratic solver forming part of our time of fall computer.

Figure 3 is a diagram showing the principle of operation of the ballistic altitude multiplier forming part of our-time of fall computer.

IReferring now to Figure l, a right angle member indicated generally by the reference numeral I0 is provided with a pair of arms I2 and I4 extending at right angles to one another. The member I0 is provided with a flange I6 which is secured to a flange I8 formed integrally with a cylindrical member 20 which is positioned between a pair of vertical guide members 22 and 24 such that the member 20 may move vertically upwardly and downwardly and `rotate between guide members 22 and 24, carrying the right angle member l0 with it. A rack 2B is pivoted by bearing 28 to the cylindrical member 20 and is adapted to move with the cylindrical member. A flexible member 30 is secured at one end to the upper end of the rack 26 and passes over a pulley 32 so that its other end may be fastened to the end of a spring 34. The other end of spring 34 is secured by member 36 to a. stationary part of the apparatus 38. The arrangement is such that the rack 26 will be biased by the spring 34 to move upwardly. A guide member 40 is positioned at one side of the rack 26. The rack teeth 42 mesh with a pinion 44 secured to a shaft 46. The arrangement is such that the pinion will prevent the rack 26 from moving to the left maintaining it against the guide member 4D so that the rack is adapted to move only in a vertical direction to rotate the pinion 44. The rotation of the pinion will be a function of the desired time of fall, the output of the computer being taken from the rotation of this pinion.

A horizontal shaft 48 is positioned to rotate in a pair of bearings 50 and 52 and is provided with screw threads VSil uponvwhich is .threadedfmnv A Ka'dsaconstant 3 positioned in a carrier 82 for movement along a horizontal direction only. The lower end of the arm l2 of the right angle member |0 engages the roller 58 and is adapted to be positioned by it. A gear segment 84 is pivoted to the reciprocating block 80 around pivot pin 86 carried by the block. The gear segment 84 is provided with gear teeth 88 which mesh with a worm 90 carried by a shaft 92 to which is secured a bevel gear 94 meshing with a bevel gear 96 carried by a shaft 98. The end of shaft 98 carries a gear which meshes with a pinion |02 formed with elongated teeth. The assembly comprising shafts 98 and 92 and their associated gears and worm is supported from and adapted to move with the block 80. The gear |02 is provided with elongated teeth so that the gear |00 will continue to mesh therewith during the relative movement between the gear |00 and the pinion |02. A shaft |04 is adapted to rotate the pinion |02. The gear segment 84 is provided with a slotA |06 in which is seated a pin |08 secured to the end of a right angle bell crank ||0 pivotedfrabout pivot pin 2. The other end of bell crank ||0 carries a pin ||4 lodged in a slot ||6 formed in block |20. The block |20 carries a pin |22 around which a roller |24 is adapted to rotate. This roller |24 contacts the other arm |4 of the right angle member |0. The block |20 is positioned for reciprocation in a horizontal direction in a pair of guide members |26 and |28 carried by a vertically movable carrier |30 which is constrained to move in a vertical direction by a lower pair of guide members |32 and |34 and an upper pair of guide members |36 and |38. Movement of the carrier |30 in a vertical direction will move the block |20 with it and hence the roller |24. Movement of the block |20 in a horizontal direction will likewise move the roller. A pin |40 is carried by the upper portion of the carrier |30 and is positioned within a slot |42 formed in one arm |44 of a bell crank indicated generally by the reference numeral |46 and pivoted about pivot pin |48. The other arm |50 of the bell crank is provided with gear teeth |52 meshing with a worm |54 carried by a shaft |56. The shaft |04 is adapted to be rotated as a function of the ballistic, that is, as a function of trail air speed X altitude through connection |58 which may be attached to a ballistic computer (not shown). The shaft |56 is adapted to be rotated through connection |60 as a function of vertical velocity through a suitable computer (not shown). The shaft is adapted to be rotated as a function of altitude through connection |62 through a suitable computer (not shown). These functions may be set in by hand if desired.

p In the consideration of Figures 2 and 3 certain symbols will be used, namely:

C is a proportionality constant, Ci is a proportionality constant, C2 is a proportionality constant, K1 is a constant,

Ki is a constant,

K4 is a constant,

B is the ballistic equalling trail air speed X altitude VH is the initial vertical velocity of the aircraft from which the missile is being dropped,

4 H is the altitude of the aircraft above the ground, g is the acceleration of gravity, t: is the time of fall which is the desired quantity to be obtained by our time of fall computer.

The proportionality constant Ci is chosen so that C'C'2=C'i2 Referring now to Figure 2, the line OQ represents the length of the arm I2 from the apex of the right angle to the point of tangency of the roller 58. The line OP represents the length of arm 4 from the apex of the right angle to the point of tangency of the roller |24. As will be demonstrated hereinafter, the horizontal distance from the point P to the point directly below the apex of the right angle, that is, the distance from the point P to the center line of the quadratic solver, may be represented by the expression The horizontal distance from point Q to the center line of the quadratic solver may be represented by CH. The vertical distance between point Q and point P may be represented by CiVH. It will be observed that the roller 58 in Figure 1 which determines the position of point Q in Figure 2 is determined as a function of H since the gear 68 which is rotated from shaft 'l0 through the member |62 meshes with gear 66 which carries the screw 54. The roller 58 is carried by the block 56 which moves in a horizontal direction along the axis of the screw 54 as a function of H. It will be observed, too, that the vertical distance between a horizontal line through Q and a horizontal line through P is determined by the position of the roller |24. This is moved in a vertical direction through shaft |56 which is rotated as the function of Vir. The rotation of the shaft |56 will rock the bell crank |45 and move the block I 30 in a vertical direction carrying the roller |24 in a vertical direction through a distance agreeable to VH. vThe vertical distance along the center line through O from the horizontal line through Q to the apex of the right angle may be designated as Clt/i7 2 In Figure 2 the right angle is divided into two angles by the vertical center line through 0. The angle formed by the center line withthe arm OP may be designated as The angle formed by the center line with the arm OQ may be designated as a. Since the angle POQ is a Substituting the values given in Equations 2 and 3 in Equation 1 We obtain 5 Cross multiplying in Equation 4 we obtain (5) C H --1[1+K.B(H+Ko1)= We have seen that CC2=C12. Substituting this value in Equation 6 and collecting terms we obtain the following equation 2 (7) 2-g+tv-H[1+K.B H+Km=0 Solving Equation 7 we obtain Let this expression equal Y and let us now refer to Figure 3. The point A represents the axis of the pivot pin ||2 of the bell crank H0. The point B represents the axis of the pin ||4 carried by one bell crank arm. The point C represents the axis of the pin |08 carried by the other bell crank arm which is lodged within the slot |06. The length of the bell crank arms are equal and are represented by the constant K1. Let the angle between the upper bell crank arm and the horizontal line through A be ip. Since the bell crank is a right angle, the angle between the vertical line through A and the other bell crank arm will likewise be o. The point D represents the axis of the pivot pin 86 around which the segment 84 rotates. Since the segment 84 is carried by the block 80 which moves in a horizontal direction as a function of altitude, the horizontal displacement between point D and a vertical line through the center of the slot |06 represents H. The distance between 'M'I'he angle between the horizontal line through A and the axis of the slot |06 is represented by KiB. It will be observed that this angle is changed as a function of B through the rotation of shaft |04 so that this angle will always be a function of B.

The following relations appear:

for small angles- YVple in construction, sure and easy Yof operation f We choose the constant K4 to have a value equal to Substituting this value for KJ. in Equation 1l we obtain Klqs 2 Now, from Figure 2 we see (13) :92E-HX@ or, substituting value of Km in 12 in Equation 13 we obtain The ballistic may be set manually for the approximate altitude and air speed at the time of drop or may be computed by cams as a function of air speed, altitude and type of bomb (which gives trail) in a computer (not shown), and this may be fed through connection |58 to determine the angle at which the slot |06 is positioned with respect to the horizontal. The altitude may be measured from an integrating altimeter and fed automatically to member |62 to rotate shafts '|0 and 48. The rotation of shaft 'l0 will position the block 80 and hence the pivot pin 8S along a horizontal line as a function of altitude. The rotation of shaft 48 will position the roller 58 as a function of altitude. The product of altitude and ballistic will determine the horizontal distance between the point P and the vertical center line through the apex of the right angle member I0 by means of the pin ||4 and the horizontally sliding block |20. The block is moved in a vertical direction as a function of VH through the bell crank |46 which is controlled by shaft |56 and the pin |40 and its coacting slot |42. The coaction of the movement of the block 20 in a horizontal direction through the BH multiplier and in a vertical direction through the VH function will position the roller |24 and determine the position of point P. The position of both points P and Q being determined in this manner will automatically position the apex of the right angle member I0 to represent the desired function tf.

It will be seen that we have accomplished the objects of our invention. We have provided a time of fall computer in which bomb trail divided by the product of air speed and altitude is used as the ballistic. We have provided a time of fall computer in which the time of fall is instantly given from settings representing altitude, ballistic and vertical velocity of the aircraft at the time of drop. Our computer is simand will continuously compute time of fall if the arguments of altitude, ballistic and vertical velocity are continuously fed into the computer. Our time of fall computer is simple and inexpensive to construct and may be manufactured to give high precision in the computation of the desired'variable.

It will be understood that certain'features and subcombinations are of utilityand may be employed without reference of other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is therefore to be understood that our invention is not to be limited to the specic details shown and described.

Having thus described our invention, what We claim is:

1. A time of fall computer for indicating the time of fall of a projectile dropped from an aircraft to the surface of the earth including in combination a bell crank having a pair of arms extending at right angles to each other, a pivot for rotating the bell crank around a point adjacent the intersection of said arms, guide means for said pivot constraining it to move along a predetermined straight line, a first positioning means adjacent one of said armsvaggsecond positioning means adjacent the other of said arms, biasing means to bring said arms into engagement with said positioning means, means for moving said first positioning means along a locus at right angles to said straight line as a function of the altitude of the aircraft, means for moving the other of said positioning means along a locus at right angles to said straight line as a function of a ballistic correction, means for displacing said last named locus as a function of the vertical velocity of the aircraft and means responsive to the movement of said pivot along the guide means for indicating the desired time of fall.

2. A time of fall computer for indicating the time of fall of a projectile dropped from an aircraft to the surface of the earth including in combination a bell crank having a pair of arms extending at right angles to each other, a pivot for rotating the bell crank around a point adjacent the intersection of said arms, guide means for said pivot constraining it to move along a predetermined straight line, a first positioning means adjacent one of said arms, a second positioning means adjacent the other of said arms, biasing means to bring said arms into engagement with said positioning means, means for moving said first positioning means along a locus at right angles to said straight line as a function of the altitude of the aircraft, means for multiplying a ballistic correction by altitude, means for introducing a ballistic correction to the multiplier, means for introducing altitude to the multiplier, means for moving the other of said positioning means along a locus at right angles to said straight line as a function of the output of said multiplying means, and means responsive to the movement of said pivot along the fgulilde means for indicating the desired time of 3. A time of fall computer for indicating the time of fall of a projectile dropped from an aircraft to the surface of the earth including in combination a bell crank having a pair of arms extending-atright" angles t'each other, a pivot for rotating the bell crank around a point adjacent the intersection of said arms, guide means for said pivot constraining it to move along a predetermined straight line, a first positioning means adjacent one of said arms, a second positioning means adjacent the other of said arms. biasing means to bring said arms into engagement with said positioning means, means for moving said rst positioning means along a locus at right angles to said straight line as a function of the altitude of the aircraft, means for multiplying a ballistic correction by altitude, means for introducing a ballistic correction to the multiplier, means for introducing altitude to the multiplier, means for moving the other of said positioning means along a locus at right angles to said straight line as a function of the output of said multiplying means, means for displacing said second positioning means along a locus parallel to said straight line as a function of the vertical velocity of said aircraft, and means responsive to the movement of said pivot along the guide means for indicating the desired time of fall.

4. A time of fall computer as in claim 2 in which said means for multiplying a ballistic correction by the altitude comprises a carriage, means for mounting said carriage for movement along a locus at right angles to said straight line, means for moving said carriage as a function of the altitude of the aircraft, a gear segment, means for pivotally mounting said gear segment on said carriage for movement therewith, a bell crank having a pair of arms extending at right angles to each other, inter-engaging means for coupling one of said arms with said gear segment, means coupling the other of said arms with said second positioning means, and means for rotating said gear segment as a function of D the ballistic correction.

5. A time of fall computer as in claim 3 in which said means for displacing said second positioning means along a locus parallel to said straight line comprises a carriage, means for mounting said carriage for movement along a locus parallel to said straight line, a member po-- sitioned in said carriage for movement therewith and slidable therein in a direction at right angles to the direction of movement of said carriage, said second positioning means being mounted on said member, and means responsive to the vertical velocity of the aircraft for moving said carriage.

MAURITS TEN BOSCH.

CARL F. SCHAEFER.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,963,907 Julius June 19, 1934 2,113,199 Raaber Apr. 5, 1938 2,210,938 Garrett Aug. 13, 1940 2,220,399 Fagerholm Nov. 5, 1940 2,596,876. Julius May 9. 1950 utf- 7 if 

